Solar panels utilize energy from the sun and convert the sun's energy to electrical power. It is important for solar panels to remain clean to maximize production from the solar panels. Cleaning large-scale photovoltaic (PV) plants or rooftop commercial PV plants can be expensive. Further, it is important to understand the required frequency and timing of cleanings to optimize performance of the PV plant and to minimize costs.
Traditional methods to measure loss of energy due to soiling of the PV system include measuring a combination of voltage and current for a specified PV panel or panels in reference to a clean PV panel. However, due to the fact that standard PV panels consist of a plurality of series-connected PV cells these measurements are limited in accuracy and are lacking in the detailed analysis of the patterns of soiling in a PV system. Alternative methods have been developed to measure soiling levels by measuring the differences in current and voltage on two single cell pv reference panels. However these methods lack the characteristic effects of soiling that are specific to a PV panel consisting of a plurality of cells mounted inside a standard PV module. The present invention seeks to solve this problem by connecting each cell of a plurality of pv cells to a Measurement Unit (FIGS. 1, 6), whereby the Isc of each cell can be measured individually providing detailed information regarding the effects of soiling at each part of the pv panel.
PV Reference Cells are typically used to establish an irradiance baseline for PV plants. The irradiance measurements provided by PV Reference Cells are used in the calculation of important performance metrics such as Performance Ratio, for PV plants of all types and sizes. A current measurement of the PV cell typically is measured at regular intervals throughout the day and in the same plane of array (POA) as the native PV panels. In this way, the PV Reference Cell provides a performance an irradiance baseline that is used to calculate the performance of the native PV system to determine if the PV system is operating to expectation.
PV reference cells are often calibrated regularly according to rigorous standards to ensure accuracy of the reference cells. The accuracy and reliability of this irradiance baseline is extremely important to the modeling, monitoring and operation of the PV plant, in order to find and diagnose problems and ensure that the PV system is being operated according to and O&M contract, as well as to ensure performance targets are being met.
However, dirt and other debris collect on the surface of the PV reference cells over time and cause discrepancies in the measurements of the PV reference cell. Often the contribution of soiling on the PV panels is overlooked due to the fact that the PV reference cells are themselves not clean and therefore include the soiling loss in the baseline irradiance measurements.
The common method for cleaning PV Reference Cells requires sending a technician to the PV plant to wipe off the cell periodically. This is both costly and impractical for the majority of PV plants, which are often located in remote locations.
Automated methods for remote cleaning of the PV Reference Cell are not readily available and tend to include complex methods that are both unreliable and/or require additional maintenance.
What is needed, therefore, is solar panel soiling monitoring system for monitoring reduced power generated by solar panels as they become contaminated by dust and dirt.